Process of catalytically hydrogenating aromatic amino compounds and products produced thereby



lfialACEMi. de Science,

(in which formula R means an aryl residue Patented Nov. 25, 1930 UNITEDfSTATES PATENT; OFFICE FELIX KLINGEMANN, or MAINKUR, NEAR rImFoRr-on-rriE-MAIN,wr EL Loin- MEL, or w nsnonr, NEARcoroemi-on-rrzs-nnmn, .nnnsr KORTEN, or FECHEN- HEIM, NEARFRANKFORT-ON-TI-IE-MAIN, Ann THEODOR Goos'r, or LEVERKUSEN,

NEAR COLOGNE-ON-TI-IE-RHINE, GERMANY, ASSIGNOBS TO I. G. FARBENINDUSTRIEAKTIENGESELLSCHAFE A CORPORATION OF GERMANY PROCESS or GATALYTICALLYHYDRQGENATINGAROMAHTIC j PRODUCTS PRODUCED HEBEBY Ammo COMPOUNDS AND NoDrawing Application filed camber-2, 192e, Serial No. 139,226, and ummcatcher 10, 19 25.

The methods hitherto known for preparing hydrogenated aromatic aminocompounds do not give satisfactory results. The hydrogenation of primaryaromatic amines as described by Ipatiew .(cf; Berichte d. DeutschenChem. Ges. ll (1908) page 991) with hydrogen and catalysts underpressure goes on veryfslowly and undesirable by-products areformed.Sabatieri and Senderens 91 have reduced secondary and tertiary aminesinthe presence of finely divided nickel in the gaseous .state, but theirresultsare far from being satisfactory as far as quantity and qualityareconcerned. (ComptJ Bend. de vol. 138, page 457). j Nowwe have found-thataromatic amino compounds of the general formula:

of the benzeneor of the naphthalene series, X means hydrogen, which maybe replaced by alkyl, aralkyl andaryl, and X means -alkyl, which may bereplaced by aralkyl, or

acyl) and. hydrogen quickly and smoothly when treated withhydrogen in aliquid phase in the presence of a hydrogenating catalyst under pressure.Nickel, cobalt, copper or ;mixtures of thesemetals oroxidesthereof,advantageously precipitated on a substratum of large surface,hereinafter referred to simply by the termbase metal hydrogenation 1catalysts, may be used as the hydrogenatingj catalysts.- In the case ofthe alkyl-, aralkylor aryl derivatives the desired hydrogenated basesare obtained immediately, whilst in the case of acyl-derivatives theacyl group may be removed by saponification, the hydrogenated basesbeing thus formed.

The products obtained by the method described above are partially newand'maybe used for the preparation of pharmaceutical H and othervaluable technical products.

The following examples illustrate our process: v i

Example 100 parts of ethylanilineare heated in an substances well themass isthen stirred. After about 20 minutes about hexahydnoethylanilineof the formula H mar-c5115 isformed. The process is then interrupted andthe product is purified by distillation. It

formsa colourless oil, which has the properties described in theliterature.

g Example? 7 M parts of ldimethylaniline are reduced under the sameconditions as described in Example 1. The hexahydrodimethylaniline ofthe formula I i V l i M m),

shows the propertiesdescribed in the literature. The same result may beobtained if the dimethylaniline is hydrogenated at a lower temperatureand pressure, but the reaction affords longer time. p g

In an analogous 'manner the homologues of the monoQanddialkylatedanilines may be hydrogenated, such as ethyl o-toluidine,diethyl-p-toluidine, the corresponding xylidine derivatives and also thealkylated and arylated naphthylamines, such as ethyl-unaphthylamine,.phenylgB-naphthylamine or benzyl-a-naphthylamine. The hydrogenatedproducts thus formed are partly new compounds; they are colourlessbodies of a strongly basic character. Generally the products of thebenzene series are hexahydrocomhot is filtered 0E from the catalyst.

pounds, those of the naphthalene series tetrahydrocompounds.

E mample 3 50 parts of acetyl-a-naphthylamine are heated with 150 partsof tetraline and 1 part of kieselguhr catalyst containing about 25%nickel in an autoclave while stirring under a hydrogen pressure of about15-30 atmospheres. The addition of hydrogen begins already at atemperature of a little above 110 G., but it is advisable to raise thetemperature to 160-180 C. When two molecules of hydrogen have beenadded, the mass while still From the filtrateacetyl-ar-tetrahydro-a-naphthylamine of the probable formula Hg 1%separates out in an already pure state in form of fine needles of themelting point 159 C. The yield is nearly quantitative.

By saponification of the acetyl product according to the usual methodsthe free artetrahydro-a-naphthylamine is obtained in form of an oil,which does not solidify at ordinary temperatures and which boils at 275C. under normal pressure.

E mample 4 50 parts of pure acetyl- 8-11aphthylamine are heated in anautoclave while stirring with 200 parts of dekaline in the presence of acatalyst containing nickel under a hydrogenpressure of about 20atmospheres. Vhen 2 molecules of hydrogen have been added the mass isfiltered. The dekaline is distilled ofl with steam. From the residue theacetyl-artetrahydro-,8-naphthylamine of the probable formula H, NHCOCHa2 can be extracted with ether. After the ether is distilled off theproduct remains in the form of an oil which solidifies'on cooling. Theacetyl compound may be saponified by treatment with hydrochloric acid.The ar-tetrahydro-B-naphthylamine thus obtained has the boiling point271-273 C. at normal pressure (Bamberger, Ber. d. Deutsch. Chem. Ges.23, p. 882, gives boiling point 27 5-277 0 0.).

Example 5 35 parts of benzoyl-B-naphthylamine parts of dekaline and 1,7part of a kieselguhr catalyst containing 15% nickel are heated in anautoclave while stirring under a hydrogen pressure of 15-30 atmospheresto about 17 0 C. Two molecules of hydrogen are absorbed very quicklyunder these conditions. When this point is reached, the operation isinterrupted. The benzoyl-ar-tetrahydro-,8- naphthylainine of theprobable formula Hg H thus obtained, which has the melting point 165167(3., yields on saponification the base already described in Example 4L.

E mample 6 If instead of the acetyl compound used in Example 3formyl-a-naphthylamine is reduced under similar conditions, the productobtained yields after saponification the samear-tetrahydro-a-naphthylamine described in Example 3.

In the same way tetrahydro-fi-naphthylamine may be obtained fromformyl-B-naphthylamine.

Also phthalic-u-naphthalide can readily be reduced according to the sameprocess. The reduction product yields after saponification the samear-tetrahydro-a-naphthylamine as described in Example 3.

is obtained. This compound is readily soluble both in alkalies and inacids. It can be recrystallized from organic solvents of a low boilingpoint. From 50% acetic acid it separates for instance in colorless fineneedles, melting at 180-182 C.

Also other bases as for instance acetylphenyl-u-naphthylamine o'rl-acetylamino-2- naphtholethylether absorb hydrogen under correspondingconditions at about 130180 C. rapidly and yield after saponificationbases, which are hydogenated in the nucleus which is not substituted bythe aminogroup.

We claim: 1. A new process of catalytically reducing I aromaticaminocompounds comprising treating aromatic amino compounds of thegeneral formula:

wherein X stands for hydrogen or an alkyl, aralkyl, or aryl group, X foran alkyl, aralkyl, or acyl group, and the Ys represent hydrogen atoms,which may be replaced by a monovalent substituent, with hydrogen underpressure in a liquid phase in the presence of a base metal hydrogenationcatalyst.

3. A new process of catalytically reducing aromatic aminocompounds ofthe benzene series comprising treating aromatic aminocompounds of thegeneral formula:

wherein X stands for hydrogen or an alkyl,

aryl, or aralkyl group, X for an alkyl, aralkyl, or 'acyl group, and Yrepresents a monovalent substituent, with hydrogen under pressure in aliquid phase in the presence of a base metal hydrogenation catalyst.

4. As new products hydrogenated aminocompounds of the benzene series ofthe general formula:

l 1 H V H: 2 wherein X stands for hydrogen or an alkyl, aryl, or aralkylgroup, X for an alkyl, aralkyl, oracyl group, and Y represents a methylgroup, which products are colorless oils of a strong basic characterwhich absorb carbonic acid from the air.

5. As a new product hexahydroethyl-ortho-toluidin of the formula:

H CH:

NBS-0:115 H H,

which is a colorless oil and which absorbs carbonic acid from the air.

In testimony whereof, we, aflix our signatures.

FELIX KLINGEMANN. WILHELM" LOMMEL. ERNST KORTEN. THEODOR GOOST.

